Method of forming return bends



July 9, 1935. R. K. HOPKINS METHOD OF FORMING RETURN BENDS Filed Feb. 8, 1933 3 Sheets-Sheet 1 6 4&7 ATTORNEYS R. K. HOPKINS 2,007,648

METHOD OF FORMING RETURN BENDS July 9, 1935.

Filed Feb. 8, 1935 3 Sheets-Sheet 2 II v U a INVENTOR \uiuizr/ K Ila 412715 BY MAW I ATTORNEYS July 9, 1935. HOPKINS 2,007,648

METHOD OF FORMING RETURN BENDS Filed Feb. 8, 1933 a Sheets-Sheet 5 Q N H w I w I II. N

I HI I 'll! N y I '1 a? J "H'- w lLl l I INN I ll ll I -N INVENTOR I ATTORNEYS Patented July 9, 193

METHOD OF FORMING RETURN BENDS Robert K. Hopkins, West Brighton, N. Y., assignor to The M. W. Kellogg 00., New York, N. Y., a.

J corporation of Delaware Application February s, 1933, Serial No. 655,719

a Claimsk (c1. 29-1575) Thisinvention relates to headers 'or return bends for interconnecting the adjacent ends of 'two or more parallel tubes. Headers 'or return bends of this type are particularly adaptedv for 5 use in connection with cracking coils and similar oil refining equipment, although their utility is not limited to this type of apparatus, The complicated shape of such headers or return bends renders it impracticable to produce them commercially by forging in a single piece. Cast headers or return bends have therefore been employed in spite of the recognized superior strength of forgings as compared with castings. The superiority of forgings over castings makes the use in cracking coils because of the extremely high pressures and temperatures frequently encountered and the subsequent strain upon the equipment.

The primary object of the invention is to provide a method of fabricating unitary headers or return bends from forged steel, whereby the obstacles heretofore encountered in forging such articles are overcome and unitary headersor in a simple and economical manner.

According to my invention, a unitary forged steel header or return bend is produced by forging the header or return bend in separate sec- 30 tions, each of which may be forged in a convenientandeconomical manner, and subsequently joining these sections by welding in such manner as to insure accurate dimensioning of the finished article. Fabricated in this manner, the header or return bend, while not forged as a complete unit, has all of the desirable characteristics of a single forging, and it is generally more satisfactory than a cast steel header or return bend, both in point of serviceand in point ofsafety. T

More specifically, each individual forging has a, body portion adapted to accommodateatube and a boss extending laterally from the-body por- 1 tion and adapted to form a cross-over connec- 45 ,tion to the next tube. A- forging of this character may be conveniently andeconomically made by, press forging as disclosed hereinafter. The bosses of two such forgings are then joined together by welding td form a double header or 50 return bend. Where a multiple tube header is to be made, forgings as just described areused at the'ends of the header, and intermediate forgings having two oppositely disposed lateral bosses are welded therebetween. As is well understood by those skilled in this art, it is essential in such of forged headers or return bends very desirable.

return bends may be produced from forged steel,

headers or return bends to have the centers of the tube bores at a specified distance apart, and my invention accomplishes this in a simple an expeditious manner.

My invention may be more clearly understood 5 by reference to the following description and to the accompanying drawings, which form a part of "this specification, and in which:

Figure 1 is a central vertical section through a die for press forging one of the individual sec- 10 tions, the plunger of the press being shown in broken lines;

Figure 2 is a side elevation of a forging made in the die shown in Figure 1;,

Figure 3 is a top plan view of the forging shown in Figure 2;

Figure 4 is a central vertical section throughthe forging shown in Figures 2 and 3 after drilling and cutting;

Figure 5 is a top plan view of the drilled and cut forging shown in Figure 4;

Figure 6 is a. side elevation showing in full lines two of the drilled and cut forgings in position for welding to produce a double header, and in broken lines the positions of the forgings after the welding operation is completed; Figure 7 is a top plan view of the parts shown in Figure 6;

Figure 8 is a central vertical section through the finished double header after machining;

Figure ii'is a side elevation of a modified forging for use in the production of multiple headers;

Figure 10 is a central vertical section through (the forging shown in Figure 9 after drilling an cutting; I Figure 11' is a central vertical section through a multiple header after the weldingv operation; and e Figure 12 is a-plan view of the header shown 40 in Figure 11. 4

Referring more particularly to the drawings, the die I shown in Figure lcomprises an upper member 2\ and 'a lower member 3 meeting in a horizontal ,plane at 4. A cylindrical opening 5 extends vertically through the upper member 2 andfregisters with a. cylindrical opening 6 extending part way into the lower member 3 to form a vertical cylindrical. recess 1. The ver-," tical cylindrical recess 1 shapes the mainbody r portion of the forging. The members 2 and 3 are also cut away as shown to form a cylindrical recess 8 extending laterally from the vertical cylindrical recess 1. The lateral recess 8 forms a cylindrical laterally extending boss on thefor'ging, and the plane 4 bisects the recess 8 to, permit subsequent removal of the forging from the die.

A removable plug 9 has a head I 0 fitting snugly in the outer end of the lateral recess 8 and has a cylindrical handle I fitting snugly in semi-cylindrical recesses I2 and I3 in the members 2 and 3, respectively. The lower member 3 and the plug 9 are preferably provided with substantially hemispherical protuberances I4 and I5 located centrally of the closed ends of the vertical cylindrical recess 1 and the lateral cylindrical recess 8, respectively. The protuberance I4 is shown as integral with the lower member 3, but it may if desired be formed-by a plug inserted in the member 3. The rear face l6 of the head In and the corresponding end of the recess 8 are preferably shaped like a frustrum of a cone, as illustrated, in order to facilitate separation of the die members from the plug 9 after the forging operation.

A plurality of plugs 9 having heads ID of different thicknesses may be provided, so that a. single die I may be used to make forgings having side bosses of different lengths, depending upon the tube center to center distance desired in the finished header.

In use, the two members of the die I are locked together in a suitable forging press with a plug 9 of suitable dimensions in place, and a heated billet, preferably a short piece of round bar steel stock, is dropped into the vertical recess 1. A plunger 20, shown in broken lines in Figure 1, is then forced downwardly into the vertical recess 1 of the die, thus forcing the hot metal to occupy all of the recesses and 8 of the die. The plunger is then raised, the die unlocked, and the upper member 2' raised, leaving the hot forging and the plug 9 resting upon the lower member 3. The forging is now lifted by means of tongs or other suitable'implement, carrying with it the inner end of the plug 9 for a short distance until the plug drops out or is extracted laterally.

The forging 2| so produced will have the shape shown in Figures 2 and 3 and will comprise a main cylindrical body portion 22 and a cylindrical side boss 23. The length of the ,boss 23 will depend upon the thickness of the head ID of the particular plug 9 chosen. The upper end of the body portion 22 will have a depression 24 corresponding in shape to the plunger 20. The lower end of the body portion 22 and the end of the boss 23 will have depressions 25 and 2G, corresponding respectively to the protuberances l4 and I5 of the die member 3 and the plug 9.

Portions of the body 22 of the forging 21 are then cut away, preferably by means of an acetylene cutting torch, to form the ears 21 and 28 having slots 23 and 30, respectively, as shown in Figures 4 and 5. These ears and slots are for the purpose of supporting the customary holding yokes. for the closure plugs ordinarily employed in equipment of this kind for sealing the outer ends of the tube bores. It will be understood that the present invention is not concerned with the particular form of closure devices utilized, and that provision might be made for any desired form of such closures.- The forging 2| is next drilled to form the tube bore 3| in the body portion 22 and the cross-over connection 32 in the ;boss 23, as likewise shown in Figures 4 and 51'" To make a double header, two of the drilled and cut forgings 2| are placed with their bosses 23 facing oneanother as shown in full lines in Figures 6 and 7. The ends ofthe bosses 23 may then be joined together by welding in any desired manner. As stated above, all headers or return bends are made for a definite spacing of the tube centers. The bosses 23 must therefore be of such length that the required distance between the center lines of the tube bores 3| is obtained after the welding operation is completed. If ordinary electric arc welding utilizing a fusible welding rod electrode is to be employed, the ends of the bosses 23 are preferably chamfered so as to form, the

usual welding groove.

Although electric arc welding may be employed as above described, in the preferred embodiment of my invention I join.the two forgings by resistance flash welding. With this type of .welding, I make the bosses 23 sufliciently long so that the distance between the center lines of the tube bore 3| is greater at the commencement of the welding operation than is desired in the finished header. Thus, the full lines 35 and 3G in Figure 7 show the spacing of the center lines of the tube bores 3| prior to welding, and the broken lines 35' and 36 show the spacing of these same center lines after the resistance flash welding operation is completed.

In this resistance flash welding, the welding current is passed directly through the two forgings, and an arc is established between the meeting faces of the bosses 23 by making contact between'the two bosses and then separating them slightly. The arc thus established heats the metal at the ends of the bosses, and after a short time this metal begins to melt. The two forgings are then fed slowly towards each other until the distance between the tube bore center lines is a predetermined amount greater than that desired in the finished header. When this predetermined point is reached, the two forgings are pushed rapidly and firmly together until a definite pressure is exerted between them. This last step extinguishes the arc, and the current is cut off after the arc has been thus extinguished. The extra distance allowed and the pressure to be exerted depend upon the size of the forgings and the welding conditions, and should be determined by experimentation in advance of quantity manufacture. When these factors are properly chosen. the distance between the tube bore center lines of the welded forgings will be within the allowable limits of tolerance.

After the welding operation, the final machining of the header or return bend is performed. The pressure of the two forgings together produces flashes or upsets 31 and 38 at the inside and outside edges of the bosses 23, as shown in broken lines in Figures 6 and '7. These flashes or upsets may be seen somewhat more clearly in Figures H and I2. The upsets 31 and 38 may be removed partially or wholly as shown in Figure 8, the outer upset 31 being removed by chipping or otherwise, and the inner upset 38 by the use of an appropriate broaching tool. At the top of the header, the seats 40 are machined very accurately to accommodate the customary closure plugs (not shown) and the tube seats 4| are also machined accurately not only as to their internal dimensions, but so as to maintain the center to center distances of the tube bores 3| within the required tolerances.

When it is desired to manufacture headers or return bends having provision for more than two tubes, forgings 50, such as shown in Figure 9, are employed in addition to the forgings 2|. The forging 50 may be made in a die similar to that shown in Figure 1 except that recesses are formed Figure 10. To make a three tube header, one forging 50 is placed between two forgings 2| and the whole welded together as shown in Figures 11 and 12. The welding operation may be performed in stages, by first welding one end forging 2| to the central forging 50, and then welding the other end forging 2| to the central forging 50, or the two welding operations maybe performed simultaneously if desired. .It will be obvious that headers for any desired number of, tubes may be made simply by inserting additional forgings 50 between the end forgings 2|. The welded forgings shown in Figures 11 and\12 should, of course, be machined subsequently to the welding operation similarly to the machined header shown in Figure 8. v

It will be apparent that my invention permits the manufacture of headers or return bends accommodating any desired number of tubes from a plurality of individual forgings each of which may be made in an economical and expeditious manner. Furthermore, my invention permits the welding of these forgings in such manner that accurate centering. of the respective forgings is obtained. The resistance welded joint of the preferred modification of my invention is formed wholly from the original forged steel of the forging, and hence the welded joint has a strength substantially the same as that of the other portions of the finished header. A further advantage of my invention is that headers of varying tube center distances may be made from the same original forgings, within reasonable limits, and where extreme variations are desired, this may be accomplished with the same die merely by changing the size of the removable plugused during the forging. operation.

It will be obvious that various modifications may be made in my invention without departing from the spirit thereof,-and I desire to be limited therefore only by the prior, art and the scope of the appended claims.

I claim:

1. The processof forming unitary press forged angularly extending from the center of said body portion for a distance substantially in excess of one half the distance between centers of the finished return bend by press shaping each of the billets; completing the formation of passageways in said blanks by connecting the hollows therein; incorporating two thus formed blanks into a re- -.turn bend structure by flash resistance welding them into a unit, said body portions being closed by press forged metal opposite their respective bosses.

2. The process of manufacturing press forged steel return bends which comprises press forging heated billets to form respective return bend blanks each having a partially hollowed body portion and a partially hollowed boss extending laterally therefrom, said boss extending from the center of said body portion in excess of one half of the predetermined distance between centers of the final return bend, completing the formation of passageways in said blanks by connecting the hollows therein, assembling two thus hollowed blanks with their bosses in abutting relation, and fiash resistance welding said two blanks to produce a unitary return bend of the. predetermined distance between centers, those walls of portion and a partially hollowed boss extending laterally therefrom, said boss extending from the center of the body portion in excess of one half the distance between centers of the final return bend, press forging heated billets to form 'respective return bend blanks each having a partially hollowed body portion and ,a pair of partially hollowed bosses extending laterally therefrom, the distancebetween the extremities .of said pair of bosses exceeding the predetermined distance between centers of the final return bend, completing the formation of passageways in said first and said second mentioned blanks by connecting the hollows therein, assembling a pair of said first mentioned blanks with their bosses in alignment, placing at least one of said second mentioned blanks between the blanks of said pair of first mentioned blanks with adjacent bosses in abutting relation, and flash resistance welding said blanks to produce a unitary return bend with the desired distance between centers, those walls of each of the end body portions opposite the respective bosses thereof being closed by press forged steel.

ROBERT K. HOPKINS. 

